Bolstered by a huge increase in cases involving heroin, the rate at which Americans die from drug overdoses has more than doubled since the end of the millennium.

The Centers for Disease Control and Prevention released data Friday showing the nation's overdose rate at 16.3 per 100,000 people in 2015 — more than 2.5 times the rate it was in 1999.

The numbers show overdose deaths afflict middle-aged adults and white people the most. Heroin leads the charge, accounting for a quarter of the overdose deaths, more than triple the rate at which it killed in 2010.

States across the country have pledged to curb drug abuse through public policy. In Wisconsin, policy makers launched an opioid task force and facilitated lower prices on an anti-overdose drug. The American Society of Addiction Medicine recently praised New Jersey Gov. Chris Christie and the state's legislature for mandating insurance cover up to six months of addiction treatment.

The states with the highest rates of drug overdose death rates were West Virginia, New Hampshire, Kentucky and Ohio. Although, 21 states outpaced the national average. Those include Pennsylvania, Massachusetts and New Mexico among others.

Overall, overdose deaths ticked up for every age group, but none more than those 55-64, who fatally overdosed at five times the rate they did 16 years prior. The group with the highest rate of deaths were those 45-54. Teens and young 20-somethings died at much smaller rates than those older than them, except those older than 65. The overdose death rates for people between 25 and 64 years old were more than twice those 15 to 24.

The rate at which white people overdosed fatally, the study found, had more than tripled since 1999. In 2015, white overdose death rates also nearly tripled those of Hispanics and nearly double African-Americans. The study found the rate at which men overdosed was "significantly higher" than women.

Heroin caused more drug overdoses than any other drug. Heroin's increase was met with decreases in drug deaths including oxycodone and methadone. The study found opioid analgesics such as oxycodone and hydrocodone dipped 5% since 2010 and methadone was down 6% over the same period. However, deaths involving cocaine went up 2%.